1. Field of the Invention
The present invention relates to several apparatuses for severing pipe and a method for severing pipe, and more particularly to apparatuses for severing downhole pipe and a method of severing downhole pipe to form a region in the well borehole devoid of downhole pipe for enhancing the performance of a perforating gun wherein such method eliminates the need for 1) removing a well head; 2) a crane or rig for raising a cut up-hole pipe; and, 3) a pump for controlling the pressure of the well.
2. General Background
Directional or vertical well boreholes are drilled to high pressure zones in the earth wherein such high pressure zones contain oil or gas. As is known, the well borehole has set therein a tubular casing. After the tubular casing is set, cement is pumped downwardly until such cement reaches the lowermost edge of the tubular casing. Thereafter, the cement flows upward between the outer surface of the tubular casing and the earth for creating a cement barrier between the earth and the tubular casing.
In some instances there are a plurality of oil or gas high pressure zones located at different depths. For exemplary purposes, a first high pressure zone may be located at 10,000 feet and a second high pressure zone may be located at 5,000 feet. In practice, a perforating gun, such as a 4 inch perforating gun, is lowered to the first high pressure zone located at 10,000 feet and shot. The projectile exiting the perforating gun of 4 inches usually provides a clear path to the high pressure zone and especially to a full potential reservoir in the high pressure zone. Thereafter, to prevent the uncontrolled spurting of the oil, exiting the first high pressure zone, at the earth's surface, the pressure in the well borehole is controlled under hydrostatic pressure.
The hydrostatic pressure is replaced with a cement packer to seal the well borehole located at a predetermined distance above the first high pressure zone but below the second high pressure zone located at 5,000 feet and a downhole pipe which extends from the earth's surface to below the packer. Therefore, the oil can be conveyed from the first high pressure zone located at 10,000 feet to the earth's surface via the downhole pipe.
After, the high pressure zone located at 10,000 feet is depleted, it is highly desirable to access the second high pressure zone located at 5,000 feet. Moreover, after the well borehole was drilled, other high pressure zones may have been determined which can also be accessed after the first high pressure zone located at 10,000 feet has been depleted. To access the second high pressure zone located at 5,000 feet a smaller perforating gun of 1.5 to 2 inches capable of fitting in the downhole pipe is lowered to the location of the second high pressure zone. The perforating gun is shot in the downhole pipe. Therefore, the projectile exiting the perforating gun must penetrate the downhole pipe suspended in the tubular casing, the tubular casing and the cement barrier. As a result, the distance traveled by the projectile exiting the perforating gun is significantly reduced and a clear path to the desire full potential reservoir of the high pressure zone located at 5,000 feet may not be had.
In some instances, if the payload of the high pressure zone is large enough, a more costly process is performed to access the second high pressure zone. This process forms a region in the well borehole devoid of down hole pipe by cutting or severing the downhole pipe and raising the upper portion of the cut downhole pipe via a rig. Since a rig costs approximately $2,000 a day and if the process takes 30 days, then the rig cost alone can be $60,000.
When cutting the downhole pipe in a well borehole, it has been the practice to lower a cutting tool into the downhole pipe to a predetermined location and to then cut or sever the downhole pipe in order to free at least the upper portion of the downhole pipe. However, sometimes the portions of the downhole pipe cut by these devices bindingly contact and cannot be separated. Thus, thy prior art cutting tools are sometimes inadequate to separate the downhole pipe. If the pipe has been properly severed, the pipe above the cut is raised, via a crane or rig, for example, 60 feet. As can be appreciated, said region in the well borehole devoid of downhole pipe has been formed. However, to raise the cut downhole pipe 1) the well head must be broken and removed; 2) a crane or rig must be deployed to raise the cut up-hole pipe; and, 3) a pump is required to control the pressure of the well.
Thereafter, a perforating gun is lowered downhole to the region in the well borehole devoid of downhole pipe. The perforating gun is positioned along the inner surface of the tubular casing and is shot. The projectile exiting the perforating gun perforates the tubular casing and the cement barrier and travels a distance for providing a path to said high pressure zone for access to the oil or gas. Thereafter, the pressure of the high pressure zone is controlled.
Several devices have been patented which are aimed at severing downhole pipe which has become lodged in a well bore and perforating guns.
EP Patent Application No. EP 0481,571-A2 of Halliburton Company teaches perforating guns for downhole well pipe that are placed at multiple levels.
U.S. Pat. No. 2,629,445 issued to John C. Kinley on the application of G. A. Dill and entitled "PIPE SEVERING METHOD AND APPARATUS" teaches a pipe severing method and apparatus that explosively perforates and cuts the pipe in a well.
U.S. Pat. No. 2,896,718 issued to Gulf Oil Corporation on the application of T. A. Kibby and entitled "METHOD AND APPARATUS FOR COMPLETING WELLS" discloses downhole perforating with an apparatus that has attachable supports for stabilization of a chemical cutter.
U.S. Pat. Nos. 4,451,487 and 4,552,234, both issued to Halliburton Company on the application of L. W. Revett, disclose well perforating apparatuses that have angled or inclined firing or perforating hole arrangements circumferentially disposed about the body. The Revett '234 patent further discloses a lower centralizing apparatus.
U.S. Pat. No. 4,799,829 issued to P. M. Kenny and entitled "METHOD AND APPARATUS FOR REMOVING SUBMERGED PLATFORMS" discloses a downhole chemical cutter that cuts piping horizontally, with stabilization means extending radially outwardly from the cutter for stabilizing it in angulated piping.
U.S. Pat. No. 2,918,125 entitled "CHEMICAL CUTTING METHOD AND APPARATUS" teaches a conventional chemical cutter having a discharge head portion coupled to a chemical container portion. The discharge head cuts in a horizontal plane.
U.S. Pat. No. 4,703,802 entitles "CUTTING AND RECOVERY TOOL" is related to a rotary cutter and recovery tool wherein the cutter comprises outwardly-pivoting cutting arms.
Other patents present in the art are U.S. Pat. No. 4,352,397 entitled "METHODS, APPARATUS AND PYROTECHNIC COMPOSITIONS FOR SEVERING CONDUITS"; U.S. Pat. No. 2,680,487 entitled "METHOD AND APPARATUS FOR WELL OPERATIONS EMPLOYING HYDROGEN PEROXIDE"; U.S. Pat. No. 3,706,344 entitled "TUBING CONVEYED PERMANENT COMPLETION METHOD AND DEVICE"; and U.S. Pat. No. 4,960,171 entitled "CHARGE PHASING ARRANGEMENTS IN A PERFORATING GUN"; all of which are directed to cutting downhole pipe, but do not meet the needs of the apparatus and method of the present invention.
Thus, a need exists for a first cutting tool for severing a downhole pipe, at an angle, to maximize the release of the potential energy stored in the severed downhole pipe located in a directional or vertical well borehole; a separating tool for separating bindingly contacted portions of a severed downhole pipe by facilitating the release of such stored potential energy; an insertable plug for sealing a portion of the upper downhole pipe portion; and, a second cutting tool for severing above the plug the plugged upper downhole pipe portion and jettisoning downward the severed bottom portion of the plugged upper downhole pipe portion.
Moreover, there exits a need for a weight biasing assembly for orientating the first cutting tool and the separating tool in the well borehole.
Furthermore, there is a need for a method of severing downhole pipe to form a region in the well borehole devoid of downhole pipe for enhancing the performance of a perforating gun wherein such method eliminates the need for 1) removing a well head; 2) a crane or rig for raising a cut up-hole pipe; and, 3) a pump for controlling the pressure of the well.
Regarding the method of severing a downhole pipe, there is a need for a method of severing a downhole pipe to form a region in the well borehole devoid of downhole pipe which comprises cutting the downhole pipe, at an angle, by a first cutting tool for maximizing the release of the stored potential energy, along the cut, by a upper downhole pipe portion and a lower downhole pipe portion; releasing the stored potential energy along the cut; releasing unexpended stored potential energy of bindingly contacted portions of the downhole pipe, by a separating tool; inserting a plug in the upper downhole pipe portion for sealing a portion of the upper downhole pipe portion; cutting the pipe above said plug via a second cutting tool; and, jettisoning downward the severed bottom portion of the plugged upper downhole pipe portion wherein such severed pipe portion becomes somewhat parallel aligned with the bottom downhole pipe portion to create a region in the well borehole devoid of downhole pipe.